1. Field of the Invention
The present invention relates generally to an automatic tool-exchanging apparatus which can make an arm extend/contract with a rational and simple structure, and which can operate at a high speed that is essentially obtainable by making a turning radius small.
2. Description of the Related Art
An automatic tool-exchanging apparatus is configured to automatically exchange a tool placed in a waiting position, such as a tool magazine, and a tool placed in an exchange position, such as a main shaft of a machining center, by rotating an arm provided on an arm-driving shaft which is driven to rotate. There has been proposed a xe2x80x9ctool exchange apparatusxe2x80x9d (refer to Japanese Patent Application Laid-open Publication No. Hei 11-99429) where the arm may be extended outwardly from or contracted back in view of an arm-driving shaft which is the center of rotation in order so that the arm is extended when it grasps a tool, and the arm is shortened when it is rotated. Especially, since the turning radius of the arm can be shortened by contracting the arm at the time of rotation, the distance between the tool magazine and the main shaft can be shortened to save space. Further, rotational inertia of the arm may be made small to provide high-speed operation of the apparatus.
The above-mentioned apparatus is configured as below. A circularly-moving portion is attached to a tool-exchanging shaft which corresponds to an arm-driving shaft. A pair of circularly-moving shafts are attached to both ends of the circularly-moving portion so as to sandwich the tool-exchanging shaft. A rotating portion is attached to the circularly-moving shafts, respectively. Further, tool grippers are attached to the respective rotating portions via a rotating shaft. The circularly-moving portion is made to move circularly by the circular movement of the tool-exchanging shaft. According to this circular movement, the rotating portion is swung around the circularly-moving shaft in respect to the circularly-moving portion. Further, the tool gripper is swung around the rotating shaft in respect to the rotating portion. Thus, the entire length from the tool-exchanging shaft to the tool gripper can be extended and shortened. For transmission of rotational movements between the respective shafts, a gear mechanism is used.
Incidentally, in the above tool exchange apparatus, a series of sections which correspond to the arm has a complex structure comprised of a circularly-moving portion, a rotating portion, a tool gripper, a circularly-moving shaft and a rotating shaft which subsequently connect the above, and a gear mechanism which transmits rotational movement to the various members to swing and oscillate them. Further, the various members and gear mechanism are required to comprise sufficient rigidity so as to ensure operation when holding a tool having considerable weight. Accordingly, the portion corresponding to the arm is thought to bear a considerable weight.
If the portion corresponding to the arm has the above-mentioned considerable weight, a considerable power loss will occur when moving the members, i.e., the portions from the circularly-moving portion to the tool gripper. Further, even though the turning radius is made smaller by drawing-in the tool gripper at the time of rotational movement, due to the weight of the portion corresponding to the arm, the rotational inertia cannot be reduced to a small amount. Therefore, it is difficult to accurately stop and position the tool gripper in the waiting position and the exchange position, and also there is a problem that it is difficult to make the apparatus operate at high speed.
The present invention is made in view of the above and other problems, and its object is to provide an automatic tool-exchanging apparatus which can make an arm extend/contract with a rational and simple structure, and which may operate at a high speed that is essentially obtainable by making the turning radius small.
An automatic tool-exchanging apparatus according to one aspect of the present invention comprises: an arm-driving shaft capable of being driven to rotate; an arm provided on the arm-driving shaft and capable of being rotated, the arm capable of being moved to extend/contract, and comprising: a grip arm for attachably/detachably holding a tool, and an arm support movably supporting the grip arm; a clutch provided between the arm support and the arm-driving shaft, the clutch capable of connecting the arm support and the arm-driving shaft to make them rotate integrally, and disconnecting the arm support and the arm-driving shaft to generate a relative rotation therebetween; and a link provided between the grip arm and the arm-driving shaft, the link capable of transmitting the relative rotation of the arm-driving shaft in respect to the arm support to make the grip arm move.
Further, in the automatic tool-exchanging apparatus, the arm-driving shaft may be driven to rotate back and forth; the clutch may generate a back-and-forth relative rotation between the arm support and the arm-driving shaft; and the link may transmit the back-and-forth relative rotation to the grip arm to make the grip arm reciprocate.
Further, in the automatic tool-exchanging apparatus, the arm-driving shaft may be driven to reciprocate in the axial direction; the arm support may be made to detachably engage a stopper according to the reciprocation in the axial direction of the arm-driving shaft, the stopper prevents the rotation of the arm support; and the clutch may be disconnected when the arm support engages the stopper.
Features and objects of the present invention other than the above will become clear by reading the description of the present specification with reference to the accompanying drawings.